Keyboard encoder ICs
Texas Instruments are known to have produced two models of single-chip keyboard encoders, TMS 5000 and TMS 5001.
|TMS 5000||90||4||ASR-33||The details are only known from a single advertisement|
|TMS 5001||90||4||10||NKRO/N-key lockout||Parallel||ASCII typewriter and bit-paired
|The four encoding options are likely to be separate parts|
Little is known about the TMS 5000. It is mentioned in US patent 3974575 filed in June 1974. An advertisement in Popular Electronics in 1977 for the “TMS-5000” (specifically TMS 5000 NL) indicates that it is a quad-mode 90-key encoder with ASR-33 output. The advertisement also mentions the “ZA 8010 C” marking as seen on the TMS 5000 NC encoder in a Clare-Pendar–manufactured Texas Instruments Silent 700 keyboard, suggesting that the chips being sold are surplus parts. However, the Clare-Pendar keyboards used TMS 5000 NC. (“NC” and “NL” are both plastic IC packages, contrasted with the ceramic “JC” and “JL”, but the meaning of “C” and “L” is not defined.)
TMS 5000 is said to be “Compatible with Reed and Mechanical Switches”, a phrase used verbatim in the TMS 5001 specifications.
By comparison, TMS 5001 is much better documented. The preliminary specifications for TMS 5001 NL are give in the Semiconductor Memory Data Book for Design Engineers from 1975. There is no indication of how TMS 5001 differs from TMS 5000. This is also a 90-key quad-mode encoder, with 10-bit output codes. Both N-key rollover and N-key lockout are offered. In N-key lockout mode, the output code is latched onto the data lines and remains so until the key is released and the next key is pressed. In N-key rollover mode, the output code is only present on the data lines briefly after the key is pressed, in order to allow the encoder to continue looking for more keys to report.
The documentation lists four output types: ASCII in both bit-paired and typewriter modes, ASR33, and Baudot paper tape punch code. With its 3600 bits of ROM and lack of any form of encoding selector, it would seem that these are separate pre-built masks, and the customer is expected to specify their choice of mask during ordering. Separate part numbers for these four variants may exist, but the databook did not list them.
- Texas Instruments TMS 5001 NL preliminary specifications, from the Semiconductor Memory Data Book for Design Engineers (1975), scanned by Bitsavers
- Electronic Parts advertisement, Popular Electronics, June 1977, from the Internet Archive